In the comparison of municipalities with respect to the medical human resources, not only the number of physicians but also the distribution of their medical practice is important. The objective of the present study was to develop an index appropriate for comparing relatively small municipalities regarding the distribution of physician's medical practice and to apply it to Nagasaki Prefecture, Japan. We modified the specialization coefficient using Bayesian smoothing technique and used it as an index for comparing all municipalities except one in Nagasaki Prefecture. We computed the modified specialization coefficient using the number of physicians by medical practice and municipality as of the end of 2000. The modified specialization coefficient showed a considerable uniformity in the proportion of physicians among municipalities, while a relatively large variation among municipalities was observed in the proportion of pediatricians and psychiatrists.